<?php 
    session_start();
    //huy session - xoa toan bo
    session_destroy();
    $url='';
    if(isset($_GET['returnUrl']) and $_GET['returnUrl']!=''){
        $url = "?returnUrl=".$_GET['returnUrl'];
    }
    //chuyen ve trang login
    header('location:login.php'.$url);
?>